gdb/gcore.c

   1 /* Generate a core file for the inferior process.
   2
   3    Copyright (C) 2001, 2002, 2003, 2004, 2005, 2006, 2007
   4    Free Software Foundation, Inc.
   5
   6    This file is part of GDB.
   7
   8    This program is free software; you can redistribute it and/or modify
   9    it under the terms of the GNU General Public License as published by
  10    the Free Software Foundation; either version 3 of the License, or
  11    (at your option) any later version.
  12
  13    This program is distributed in the hope that it will be useful,
  14    but WITHOUT ANY WARRANTY; without even the implied warranty of
  15    MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
  16    GNU General Public License for more details.
  17
  18    You should have received a copy of the GNU General Public License
  19    along with this program.  If not, see <http://www.gnu.org/licenses/>.  */
  20
  21 #include "defs.h"
  22 #include "elf-bfd.h"
  23 #include "infcall.h"
  24 #include "inferior.h"
  25 #include "gdbcore.h"
  26 #include "objfiles.h"
  27 #include "symfile.h"
  28
  29 #include "cli/cli-decode.h"
  30
  31 #include "gdb_assert.h"
  32
  33 /* The largest amount of memory to read from the target at once.  We
  34    must throttle it to limit the amount of memory used by GDB during
  35    generate-core-file for programs with large resident data.  */
  36 #define MAX_COPY_BYTES (1024 * 1024)
  37
  38 static char *default_gcore_target (void);
  39 static enum bfd_architecture default_gcore_arch (void);
  40 static unsigned long default_gcore_mach (void);
  41 static int gcore_memory_sections (bfd *);
  42
  43 /* Generate a core file from the inferior process.  */
  44
  45 static void
  46 gcore_command (char *args, int from_tty)
  47 {
  48   struct cleanup *old_chain;
  49   char *corefilename, corefilename_buffer[40];
  50   asection *note_sec = NULL;
  51   bfd *obfd;
  52   void *note_data = NULL;
  53   int note_size = 0;
  54
  55   /* No use generating a corefile without a target process.  */
  56   if (!target_has_execution)
  57     noprocess ();
  58
  59   if (args && *args)
  60     corefilename = args;
  61   else
  62     {
  63       /* Default corefile name is "core.PID".  */
  64       sprintf (corefilename_buffer, "core.%d", PIDGET (inferior_ptid));
  65       corefilename = corefilename_buffer;
  66     }
  67
  68   if (info_verbose)
  69     fprintf_filtered (gdb_stdout,
  70                       "Opening corefile '%s' for output.\n", corefilename);
  71
  72   /* Open the output file.  */
  73   obfd = bfd_openw (corefilename, default_gcore_target ());
  74   if (!obfd)
  75     error (_("Failed to open '%s' for output."), corefilename);
  76
  77   /* Need a cleanup that will close the file (FIXME: delete it?).  */
  78   old_chain = make_cleanup_bfd_close (obfd);
  79
  80   bfd_set_format (obfd, bfd_core);
  81   bfd_set_arch_mach (obfd, default_gcore_arch (), default_gcore_mach ());
  82
  83   /* An external target method must build the notes section.  */
  84   note_data = target_make_corefile_notes (obfd, &note_size);
  85
  86   /* Create the note section.  */
  87   if (note_data != NULL && note_size != 0)
  88     {
  89       note_sec = bfd_make_section_anyway_with_flags (obfd, "note0",
  90                                                      SEC_HAS_CONTENTS
  91                                                      | SEC_READONLY
  92                                                      | SEC_ALLOC);
  93       if (note_sec == NULL)
  94         error (_("Failed to create 'note' section for corefile: %s"),
  95                bfd_errmsg (bfd_get_error ()));
  96
  97       bfd_set_section_vma (obfd, note_sec, 0);
  98       bfd_set_section_alignment (obfd, note_sec, 0);
  99       bfd_set_section_size (obfd, note_sec, note_size);
 100     }
 101
 102   /* Now create the memory/load sections.  */
 103   if (gcore_memory_sections (obfd) == 0)
 104     error (_("gcore: failed to get corefile memory sections from target."));
 105
 106   /* Write out the contents of the note section.  */
 107   if (note_data != NULL && note_size != 0)
 108     {
 109       if (!bfd_set_section_contents (obfd, note_sec, note_data, 0, note_size))
 110         warning (_("writing note section (%s)"), bfd_errmsg (bfd_get_error ()));
 111     }
 112
 113   /* Succeeded.  */
 114   fprintf_filtered (gdb_stdout, "Saved corefile %s\n", corefilename);
 115
 116   /* Clean-ups will close the output file and free malloc memory.  */
 117   do_cleanups (old_chain);
 118   return;
 119 }
 120
 121 static unsigned long
 122 default_gcore_mach (void)
 123 {
 124 #if 1   /* See if this even matters...  */
 125   return 0;
 126 #else
 127
 128   const struct bfd_arch_info *bfdarch = gdbarch_bfd_arch_info (current_gdbarch);
 129
 130   if (bfdarch != NULL)
 131     return bfdarch->mach;
 132   if (exec_bfd == NULL)
 133     error (_("Can't find default bfd machine type (need execfile)."));
 134
 135   return bfd_get_mach (exec_bfd);
 136 #endif /* 1 */
 137 }
 138
 139 static enum bfd_architecture
 140 default_gcore_arch (void)
 141 {
 142   const struct bfd_arch_info * bfdarch = gdbarch_bfd_arch_info
 143                                          (current_gdbarch);
 144
 145   if (bfdarch != NULL)
 146     return bfdarch->arch;
 147   if (exec_bfd == NULL)
 148     error (_("Can't find bfd architecture for corefile (need execfile)."));
 149
 150   return bfd_get_arch (exec_bfd);
 151 }
 152
 153 static char *
 154 default_gcore_target (void)
 155 {
 156   /* FIXME: This may only work for ELF targets.  */
 157   if (exec_bfd == NULL)
 158     return NULL;
 159   else
 160     return bfd_get_target (exec_bfd);
 161 }
 162
 163 /* Derive a reasonable stack segment by unwinding the target stack,
 164    and store its limits in *BOTTOM and *TOP.  Return non-zero if
 165    successful.  */
 166
 167 static int
 168 derive_stack_segment (bfd_vma *bottom, bfd_vma *top)
 169 {
 170   struct frame_info *fi, *tmp_fi;
 171
 172   gdb_assert (bottom);
 173   gdb_assert (top);
 174
 175   /* Can't succeed without stack and registers.  */
 176   if (!target_has_stack || !target_has_registers)
 177     return 0;
 178
 179   /* Can't succeed without current frame.  */
 180   fi = get_current_frame ();
 181   if (fi == NULL)
 182     return 0;
 183
 184   /* Save frame pointer of TOS frame.  */
 185   *top = get_frame_base (fi);
 186   /* If current stack pointer is more "inner", use that instead.  */
 187   if (gdbarch_inner_than (get_frame_arch (fi), get_frame_sp (fi), *top))
 188     *top = get_frame_sp (fi);
 189
 190   /* Find prev-most frame.  */
 191   while ((tmp_fi = get_prev_frame (fi)) != NULL)
 192     fi = tmp_fi;
 193
 194   /* Save frame pointer of prev-most frame.  */
 195   *bottom = get_frame_base (fi);
 196
 197   /* Now canonicalize their order, so that BOTTOM is a lower address
 198      (as opposed to a lower stack frame).  */
 199   if (*bottom > *top)
 200     {
 201       bfd_vma tmp_vma;
 202
 203       tmp_vma = *top;
 204       *top = *bottom;
 205       *bottom = tmp_vma;
 206     }
 207
 208   return 1;
 209 }
 210
 211 /* Derive a reasonable heap segment for ABFD by looking at sbrk and
 212    the static data sections.  Store its limits in *BOTTOM and *TOP.
 213    Return non-zero if successful.  */
 214
 215 static int
 216 derive_heap_segment (bfd *abfd, bfd_vma *bottom, bfd_vma *top)
 217 {
 218   bfd_vma top_of_data_memory = 0;
 219   bfd_vma top_of_heap = 0;
 220   bfd_size_type sec_size;
 221   struct value *zero, *sbrk;
 222   bfd_vma sec_vaddr;
 223   asection *sec;
 224
 225   gdb_assert (bottom);
 226   gdb_assert (top);
 227
 228   /* This function depends on being able to call a function in the
 229      inferior.  */
 230   if (!target_has_execution)
 231     return 0;
 232
 233   /* The following code assumes that the link map is arranged as
 234      follows (low to high addresses):
 235
 236      ---------------------------------
 237      | text sections                 |
 238      ---------------------------------
 239      | data sections (including bss) |
 240      ---------------------------------
 241      | heap                          |
 242      --------------------------------- */
 243
 244   for (sec = abfd->sections; sec; sec = sec->next)
 245     {
 246       if (bfd_get_section_flags (abfd, sec) & SEC_DATA
 247           || strcmp (".bss", bfd_section_name (abfd, sec)) == 0)
 248         {
 249           sec_vaddr = bfd_get_section_vma (abfd, sec);
 250           sec_size = bfd_get_section_size (sec);
 251           if (sec_vaddr + sec_size > top_of_data_memory)
 252             top_of_data_memory = sec_vaddr + sec_size;
 253         }
 254     }
 255
 256   /* Now get the top-of-heap by calling sbrk in the inferior.  */
 257   if (lookup_minimal_symbol ("sbrk", NULL, NULL) != NULL)
 258     {
 259       sbrk = find_function_in_inferior ("sbrk");
 260       if (sbrk == NULL)
 261         return 0;
 262     }
 263   else if (lookup_minimal_symbol ("_sbrk", NULL, NULL) != NULL)
 264     {
 265       sbrk = find_function_in_inferior ("_sbrk");
 266       if (sbrk == NULL)
 267         return 0;
 268     }
 269   else
 270     return 0;
 271
 272   zero = value_from_longest (builtin_type_int, 0);
 273   gdb_assert (zero);
 274   sbrk = call_function_by_hand (sbrk, 1, &zero);
 275   if (sbrk == NULL)
 276     return 0;
 277   top_of_heap = value_as_long (sbrk);
 278
 279   /* Return results.  */
 280   if (top_of_heap > top_of_data_memory)
 281     {
 282       *bottom = top_of_data_memory;
 283       *top = top_of_heap;
 284       return 1;
 285     }
 286
 287   /* No additional heap space needs to be saved.  */
 288   return 0;
 289 }
 290
 291 static void
 292 make_output_phdrs (bfd *obfd, asection *osec, void *ignored)
 293 {
 294   int p_flags = 0;
 295   int p_type;
 296
 297   /* FIXME: these constants may only be applicable for ELF.  */
 298   if (strncmp (bfd_section_name (obfd, osec), "load", 4) == 0)
 299     p_type = PT_LOAD;
 300   else
 301     p_type = PT_NOTE;
 302
 303   p_flags |= PF_R;      /* Segment is readable.  */
 304   if (!(bfd_get_section_flags (obfd, osec) & SEC_READONLY))
 305     p_flags |= PF_W;    /* Segment is writable.  */
 306   if (bfd_get_section_flags (obfd, osec) & SEC_CODE)
 307     p_flags |= PF_X;    /* Segment is executable.  */
 308
 309   bfd_record_phdr (obfd, p_type, 1, p_flags, 0, 0, 0, 0, 1, &osec);
 310 }
 311
 312 static int
 313 gcore_create_callback (CORE_ADDR vaddr, unsigned long size,
 314                        int read, int write, int exec, void *data)
 315 {
 316   bfd *obfd = data;
 317   asection *osec;
 318   flagword flags = SEC_ALLOC | SEC_HAS_CONTENTS | SEC_LOAD;
 319
 320   /* If the memory segment has no permissions set, ignore it, otherwise
 321      when we later try to access it for read/write, we'll get an error
 322      or jam the kernel.  */
 323   if (read == 0 && write == 0 && exec == 0)
 324     {
 325       if (info_verbose)
 326         {
 327           fprintf_filtered (gdb_stdout, "Ignore segment, %s bytes at 0x%s\n",
 328                            paddr_d (size), paddr_nz (vaddr));
 329         }
 330
 331       return 0;
 332     }
 333
 334   if (write == 0)
 335     {
 336       /* See if this region of memory lies inside a known file on disk.
 337          If so, we can avoid copying its contents by clearing SEC_LOAD.  */
 338       struct objfile *objfile;
 339       struct obj_section *objsec;
 340
 341       ALL_OBJSECTIONS (objfile, objsec)
 342         {
 343           bfd *abfd = objfile->obfd;
 344           asection *asec = objsec->the_bfd_section;
 345           bfd_vma align = (bfd_vma) 1 << bfd_get_section_alignment (abfd,
 346                                                                     asec);
 347           bfd_vma start = objsec->addr & -align;
 348           bfd_vma end = (objsec->endaddr + align - 1) & -align;
 349           /* Match if either the entire memory region lies inside the
 350              section (i.e. a mapping covering some pages of a large
 351              segment) or the entire section lies inside the memory region
 352              (i.e. a mapping covering multiple small sections).
 353
 354              This BFD was synthesized from reading target memory,
 355              we don't want to omit that.  */
 356           if (((vaddr >= start && vaddr + size <= end)
 357                || (start >= vaddr && end <= vaddr + size))
 358               && !(bfd_get_file_flags (abfd) & BFD_IN_MEMORY))
 359             {
 360               flags &= ~SEC_LOAD;
 361               flags |= SEC_NEVER_LOAD;
 362               goto keep;        /* break out of two nested for loops */
 363             }
 364         }
 365
 366     keep:
 367       flags |= SEC_READONLY;
 368     }
 369
 370   if (exec)
 371     flags |= SEC_CODE;
 372   else
 373     flags |= SEC_DATA;
 374
 375   osec = bfd_make_section_anyway_with_flags (obfd, "load", flags);
 376   if (osec == NULL)
 377     {
 378       warning (_("Couldn't make gcore segment: %s"),
 379                bfd_errmsg (bfd_get_error ()));
 380       return 1;
 381     }
 382
 383   if (info_verbose)
 384     {
 385       fprintf_filtered (gdb_stdout, "Save segment, %s bytes at 0x%s\n",
 386                         paddr_d (size), paddr_nz (vaddr));
 387     }
 388
 389   bfd_set_section_size (obfd, osec, size);
 390   bfd_set_section_vma (obfd, osec, vaddr);
 391   bfd_section_lma (obfd, osec) = 0; /* ??? bfd_set_section_lma?  */
 392   return 0;
 393 }
 394
 395 static int
 396 objfile_find_memory_regions (int (*func) (CORE_ADDR, unsigned long,
 397                                           int, int, int, void *),
 398                              void *obfd)
 399 {
 400   /* Use objfile data to create memory sections.  */
 401   struct objfile *objfile;
 402   struct obj_section *objsec;
 403   bfd_vma temp_bottom, temp_top;
 404
 405   /* Call callback function for each objfile section.  */
 406   ALL_OBJSECTIONS (objfile, objsec)
 407     {
 408       bfd *ibfd = objfile->obfd;
 409       asection *isec = objsec->the_bfd_section;
 410       flagword flags = bfd_get_section_flags (ibfd, isec);
 411       int ret;
 412
 413       if ((flags & SEC_ALLOC) || (flags & SEC_LOAD))
 414         {
 415           int size = bfd_section_size (ibfd, isec);
 416           int ret;
 417
 418           ret = (*func) (objsec->addr, bfd_section_size (ibfd, isec),
 419                          1, /* All sections will be readable.  */
 420                          (flags & SEC_READONLY) == 0, /* Writable.  */
 421                          (flags & SEC_CODE) != 0, /* Executable.  */
 422                          obfd);
 423           if (ret != 0)
 424             return ret;
 425         }
 426     }
 427
 428   /* Make a stack segment.  */
 429   if (derive_stack_segment (&temp_bottom, &temp_top))
 430     (*func) (temp_bottom, temp_top - temp_bottom,
 431              1, /* Stack section will be readable.  */
 432              1, /* Stack section will be writable.  */
 433              0, /* Stack section will not be executable.  */
 434              obfd);
 435
 436   /* Make a heap segment. */
 437   if (derive_heap_segment (exec_bfd, &temp_bottom, &temp_top))
 438     (*func) (temp_bottom, temp_top - temp_bottom,
 439              1, /* Heap section will be readable.  */
 440              1, /* Heap section will be writable.  */
 441              0, /* Heap section will not be executable.  */
 442              obfd);
 443
 444   return 0;
 445 }
 446
 447 static void
 448 gcore_copy_callback (bfd *obfd, asection *osec, void *ignored)
 449 {
 450   bfd_size_type size, total_size = bfd_section_size (obfd, osec);
 451   file_ptr offset = 0;
 452   struct cleanup *old_chain = NULL;
 453   void *memhunk;
 454
 455   /* Read-only sections are marked; we don't have to copy their contents.  */
 456   if ((bfd_get_section_flags (obfd, osec) & SEC_LOAD) == 0)
 457     return;
 458
 459   /* Only interested in "load" sections.  */
 460   if (strncmp ("load", bfd_section_name (obfd, osec), 4) != 0)
 461     return;
 462
 463   size = min (total_size, MAX_COPY_BYTES);
 464   memhunk = xmalloc (size);
 465   /* ??? This is crap since xmalloc should never return NULL.  */
 466   if (memhunk == NULL)
 467     error (_("Not enough memory to create corefile."));
 468   old_chain = make_cleanup (xfree, memhunk);
 469
 470   while (total_size > 0)
 471     {
 472       if (size > total_size)
 473         size = total_size;
 474
 475       if (target_read_memory (bfd_section_vma (obfd, osec) + offset,
 476                               memhunk, size) != 0)
 477         {
 478           warning (_("Memory read failed for corefile section, %s bytes at 0x%s."),
 479                    paddr_d (size), paddr (bfd_section_vma (obfd, osec)));
 480           break;
 481         }
 482       if (!bfd_set_section_contents (obfd, osec, memhunk, offset, size))
 483         {
 484           warning (_("Failed to write corefile contents (%s)."),
 485                    bfd_errmsg (bfd_get_error ()));
 486           break;
 487         }
 488
 489       total_size -= size;
 490       offset += size;
 491     }
 492
 493   do_cleanups (old_chain);      /* Frees MEMHUNK.  */
 494 }
 495
 496 static int
 497 gcore_memory_sections (bfd *obfd)
 498 {
 499   if (target_find_memory_regions (gcore_create_callback, obfd) != 0)
 500     return 0;                   /* FIXME: error return/msg?  */
 501
 502   /* Record phdrs for section-to-segment mapping.  */
 503   bfd_map_over_sections (obfd, make_output_phdrs, NULL);
 504
 505   /* Copy memory region contents.  */
 506   bfd_map_over_sections (obfd, gcore_copy_callback, NULL);
 507
 508   return 1;
 509 }
 510
 511 void
 512 _initialize_gcore (void)
 513 {
 514   add_com ("generate-core-file", class_files, gcore_command, _("\
 515 Save a core file with the current state of the debugged process.\n\
 516 Argument is optional filename.  Default filename is 'core.<process_id>'."));
 517
 518   add_com_alias ("gcore", "generate-core-file", class_files, 1);
 519   exec_set_find_memory_regions (objfile_find_memory_regions);
 520 }